How do you grant iot:DescribeEndpoint to a lambda?

Question

How do you add an action to a default lambda role?

```
        const p = new iam.ServicePrincipal('lambda.amazonaws.com');
        const role = new iam.Role(this, "someExecRoleID", {
                roleName: "someExecRole",
                assumedBy: p
            });
        role.grant(p, "iot:DescribeEndpoint");

const serviceLambda = new nodejs.NodejsFunction(this, "WashnetEndpoints", {
                /* stuff deleted */
                handler: "getMqttEndpoint",
                role: role,
            }
        );
```

Is this because I'm assuming the lambda.aws.com service principal?

```
"AccessDeniedException: User: arn:aws:sts::312345678:assumed-role/blah is not authorized to perform: iot:DescribeEndpoint because no identity-based policy allows the iot:DescribeEndpoint action",
```

Accepted Answer

Found the documentation (that's often the hardest part!) ... seems like resource '*' is what's required.

Answer

Unless there is some security problem with what I did, I think I figured it out:

```
        const role = new iam.Role(this,
            "myExecRole_id", {
                roleName: "myExecRole",
                assumedBy: p
            });
        role.attachInlinePolicy(new iam.Policy(this, 'describe-endpoint-policy', {
            statements: [new iam.PolicyStatement({
                actions: ['iot:DescribeEndpoint'],
                resources: [*]
            })],
        }));
```

though I feel like the resource should be something specific to my account, like
```
resources: [`arn:aws:iot:*:${this.env.account}:*`]`
```

That, however, is not correct.  The ARN *service* must not be 'iot' .  Maybe it does not matter because the action starts iot: but it seems like I should want to specify a more specific resource than * here?

How do you grant iot:DescribeEndpoint to a lambda?

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